fma(3) Library Functions Manual fma(3)
NAME
fma, fmaf, fmal - floating-point multiply and add
LIBRARY
Math library (libm, -lm)
SYNOPSIS
#include <math.h>
double fma(double x, double y, double z);
float fmaf(float x, float y, float z);
long double fmal(long double x, long double y, long double z);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
fma(), fmaf(), fmal():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
DESCRIPTION
These functions compute x * y + z. The result is rounded as one ternary
operation according to the current rounding mode (see fenv(3)).
RETURN VALUE
These functions return the value of x * y + z, rounded as one ternary
operation.
If x or y is a NaN, a NaN is returned.
If x times y is an exact infinity, and z is an infinity with the oppo-
site sign, a domain error occurs, and a NaN is returned.
If one of x or y is an infinity, the other is 0, and z is not a NaN, a
domain error occurs, and a NaN is returned.
If one of x or y is an infinity, and the other is 0, and z is a NaN, a
domain error occurs, and a NaN is returned.
If x times y is not an infinity times zero (or vice versa), and z is a
NaN, a NaN is returned.
If the result overflows, a range error occurs, and an infinity with the
correct sign is returned.
If the result underflows, a range error occurs, and a signed 0 is re-
turned.
ERRORS
See math_error(7) for information on how to determine whether an error
has occurred when calling these functions.
The following errors can occur:
Domain error: x * y + z, or x * y is invalid and z is not a NaN
An invalid floating-point exception (FE_INVALID) is raised.
Range error: result overflow
An overflow floating-point exception (FE_OVERFLOW) is raised.
Range error: result underflow
An underflow floating-point exception (FE_UNDERFLOW) is raised.
These functions do not set errno.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│ fma(), fmaf(), fmal() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
C11, POSIX.1-2008.
HISTORY
glibc 2.1. C99, POSIX.1-2001.
SEE ALSO
remainder(3), remquo(3)
Linux man-pages 6.9.1 2024-05-02 fma(3)
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